This question was not a popular question with the candidates as they could not properly state the difference between tropic movements and nastic ,movements and could not explain the processes by which light brings about movement in the stem and the root of a flowering plant or the functions of the pituitary gland.
. The candidates could however state that when a seedling is placed horizontally the root will grow down and the shoot will grow up, they could also state differences between growth in plants and animals. Expected responses for questions in which they performed poorly are:
Differences between Tropic and Nastic Movement
Tropic movement Nastic movement
- it is a growth movement; - not a growth movement;
- responds to unilateral stimulus; - responds to diffuse stimulus
- slow responses; - fast responses;
- not reversible; - reversible;
- not due to cell turgor; - due to changes in cell turgor;
- directional/positive/negative - non directional/neither positive
-nor negative response.
Light - Tropic movements in Stem
- when unilateral light falls on the stem;
- the auxin/growth hormone/IAA is displaced;
- from the lighted to the dark side;
- the increase in auxin concentration on the dark side increases growth on that side;
- causing the stem to bend towards the light/positive phototropism.
Roots
- the auxin is displaced from the lighted side;
- to the dark side;
- the increase in auxin concentration retards growth on the dark side;
- causing the root to bend away from the light/negative phototropism.
Functions of Pituitary gland
- stimulates growth/growth of long bones/cell division;
- stimulates production of sex-hormones/named sex hormones; .
- stimulates production of anti-directive hormone/ ADH/regulation of water reabsorption in the kidney/osmoregulation;
- produces hormones which control other endocrine glands/stimulates thyroid gland/adrenal cortex;
- stimulates protein synthesis;
- induces birth by contraction of uterine muscles/production of oxytoxin;
- induces milk secretion/produces prolactin;
- controls egg and sperm production.
